This application seeks support for a secondary analysis of four large longitudinal datasets that measure socio-economic experiences and cognitive factors at various points in the life-span. The main objective of the proposed research is to examine several theoretical hypotheses tied to two competing explanatory models for the explanation of SES-cognitive score relationships: a) models of cognitive selection into educational levels and occupational roles, and b) models of cognitive adaptation to socio-economic change. The specific objectives are: 1) to estimate the nature of the relationship of socio-economic factors to cognitive scores at several points over the life-span, 2) to further refine empirical estimates of the extent of cognitive selection in SES-test score correlations in the early adult years, 3) to estimate the extent of cognitive adaptation to socio-economic change over the life course, 4) to address questions regarding the sources of change and stability in cognitive traits, via molar stability estimates from short- term panel data replicating measures of cognitive scores, 5) to address the additional and related question of cohort stability and change in these processes, using replicated cross-sectional data, and 6) to examine the extent of differences in patterns of relationships and parameter estimates by gender and race/ethnic categories, where possible. To accomplish these tasks, we seek support to analyze the following datasets; 1) the Wisconsin Longitudinal Study (WLS), a sample of 1957 high school graduates from the state of Wisconsin (n=8,493), followed from youth to approximately age 52 in 1992-93; 2) the Detroit Longitudinal Study of Families, a sample of young adults born in Detroit in 1961 and studied on several occasions from birth to age 32 (n=932); 3) the Health and Retirement Study (HRS), a national panel study of pre- retirement men and women aged 51-61 assessed in 1992 (n=9,824), and reinterviewed in 1994 and 1996; 4) a set of 13 nationally representative cross-sectional surveys from the General Social Surveys (n=23,076), which obtained measures of cognitive skills. Each taken by itself, these datasets cannot address the broad range of issues raised in this study, but we propose an analysis involving their combined use that will reveal the role of early-formed cognitive abilities in socio-economic achievement across the life-span, the effects of cohort experiences on cognitive development, and the adaptive potential of cognitive skills to change in response to socio-economic experiences.